The philosophy of and features desired in new musical instruments are discussed in Melville Clark, PROPOSED KEYBOARD MUSICAL INSTRUMENT, J. Acoust. Soc. Am., 31, 403-419 (1959). The instruments conceived there, in a preceding patent application Ser. No. 148,514, dated June 1, 1971, and here are real time, electronic systems on which a player may perform. The instruments are controlled by keys or pedals on which it is possible to play many notes simultaneously (multitonal capability) with one or more tone colors (multitimbral). In musical instruments belonging to this class, it is necessary to provide a separate tone generator, such as an oscillator or frequency divider element, for each note. Further, such an organization severely limits the resources that can be provided to generate and control the tone color of each note because of the cost involved. Usually these resources are limited to those that can serve all notes in common associated with a particular tone color.
In practice, it is observed that a keyboard instrument is provided with many more keys and pedals than are ever sounding, much less played, at any one moment. Thus, the equipment serving most of the notes lies idle most of the time. For example, a practical instrument may be provided with two 88 note keyboards and one 32 note pedalboard or 208 notes in all. A reasonable upper limit to the number of notes that can be played at any one time is 14, because a person has only 10 fingers and 2 feet. (He might play as many as 4 notes with 2 feet using both his heel and toe of each foot. It is recognized that more than one note may be played by a finger or toe or heel on very rare occasions. It will be seen that this possibility can be accommodated. A search of literature for pipe organs reveals that at most 12 notes are in practice ever required to be played simultaneously, and this requirement is very rare indeed.) Thus, approximately 14 (208/14 .apprxeq.14) times as many notes are provided as a player can possibly actuate at any one time. Of course, for a few tuned, percussive instruments with a long decay, e.g., vibraphone, harp, or sostenuto piano, more notes will be sounding than played. There might perhaps be as many as 20 or even 25 notes sounding simultaneously (say 3 notes per octave, 7 or 8 octaves for a very long arpeggio), but even for this extreme case, the number of notes sounding is much less than the number of notes provided and greater than can probably be perceptually appreciated.
A preceding patent application Ser. No. 148,514, dated June 1, 1971, disclosed a switching system that made it necessary to provide only as many tone generators as the maximum number of such generators that one desires to sound at any one time. This switching system is sufficiently simple that far greater resources at a given cost can be associated with each note of the instrument for the generation and control of the timbres associated with that note. Further, since usually one can accept a limit of 4 or fewer notes being sounded simultaneously for the nonpercussive instrument sounds and perhaps 12 or so for the sustained, tuned percussive sounds, it is possible to design practical instruments with even greater reduction in complexity.
In order to create an instrument with which the player can artistically express himself, it is vital that information relating to the force with which a note is depressed, the speed with which it is depressed, the sidewise force or displacement of the key, and so forth be transmissible to the sound generators in order to control the instantaneous intensity with which the note sounds, the waveshape, and the instantaneous frequency of the note, which may depart from the nominal frequency associated with the note. Most systems confine themselves to merely communicating ON/OFF information to the sound generators and are gravely lacking in expressiveness. Other systems may provide some primitive expressiveness.
The structuring of the present class of instruments is then very different from that of the usual electric organ, synthesizer, or what have you. Basically, the switching system connects a tone generator only to a note that is depressed. Thus, only as many tone generators need be provided as notes that are simultaneously sounding. Only a small number of connections need to be provided to the keying system. The generation of new and unusual sounds is trivially facilitated. Sound generators compatible with electronic music studio equipment are made possible A monotonal capability is feasible in which only one note can be sounded on a particular clavier at any given time. The addition of more tone colors is simple and major modifications are obviated. The design is inherently modular. The frequencies of the notes of a clavier may be easily changed over a wide range. Thus, one may readily tune the instrument to different frequency standards. Transposition is easily accomplished automatically by the instrument so that the performer need not be burdened with this choice. A clavier may be divided in timbre, one tone color being provided at one end and another being provided at the other end. Thus, without adding to the complexity, advantage may be taken of the fact that some simulated instruments require 80 or more different notes, whereas others require as few as 12. It is practical to provide a clavier individual to each timbre. Tunings in other temperaments are easily achieved. For example, a piano is commonly tuned to a modified equal temperament, called the Railsbeck stretched scale, in which the low notes are somewhat lower and the high notes somewhat higher than would be dictated by strict adherence to an equal tempered scale. The keyboard interval may be easily changed to a microtonal scale. Separate power amplifiers and speakers can be used for each note sounded. Thus, since the partials of many musical sounds are harmonic and since harmonic distortion is much less perceivable than intermodulation distortion, efficient and inexpensive loudspeakers can be used. Interharmonic distortion will be absent simply because no partial nonharmonically related to any other is presented to a particular loudspeaker. Truly independent tone colors can be generated when several instruments play the same note (doubling). This is essential; the waveforms will be phase incoherent. With many designs, the several waveforms are phase coherent, and a tone color is created that is the average of the tone colors of the several instruments doubling each other. It is practical to provide noncontacting keys and/or pedals. These are relatively free of wear compared with other keying methods and free of electrical and acoustic noise problems. The sounds produced may be controlled by the speed with which a key or pedal is depressed. This makes possible intensity control of percussive instruments and attack control of nonpercussive instruments. The sounds produced may also be controlled by the force with which a key or pedal is depressed. This feature can be used for the intensity and/or timbre control of nonpercussive instruments. The same transducer may be used for speed sensing, force sensing, and ON/OFF control, thereby reducing costs. Two independent sensors can be accommodated by each key or pedal without any basic circuit modification. Either key and/or pedal or external control of percussion sustain provides a sostenuto feature for the percussive instruments. Glissandos may be played easily and precisely by controlling the forces of depression of two notes when the instrument is in the glissando mode. A natural, sustained decay transient of the proper frequency can be produced after the related note is released. Sustained, percussion sounds of the proper frequency can be produced.
The present invention is an improvement of that previously disclosed in patent application Ser. No. 146,514, dated June 1, 1971.